Generally, a vehicle using an internal combustion engine consuming gasoline or heavy oil as a main fuel has an effect on air pollution.
Therefore, in order to reduce the generation of the pollution, many efforts to develop an electric vehicle or a hybrid vehicle have been made.
The electric vehicle is a vehicle using a battery motor operated by electric energy output from a battery.
Since the electric vehicle uses the battery in which a plurality of secondary cells that are rechargeable are formed as one pack as a main power source, the electric vehicle has an advantage that exhaust gas is not present and noise is reduced.
Meanwhile, the hybrid vehicle, which is a vehicle in an intermediate stage between the vehicle using the internal combustion engine and the electric vehicle, is a vehicle using two or more power sources, for example, an internal combustion engine and an electric battery.
Currently, a hybrid vehicle using the internal combustion engine and a fuel cell directly obtaining electrical energy by generating a chemical reaction while continuously supplying hydrogen and oxygen or using a battery and a fuel cell has been developed.
In the vehicle using the battery motor as described above, the number of secondary cells has been gradually increased in order to improve a power source, and a method for controlling cell balancing capable of efficiently managing a plurality of cells and packs connected to each other is required in a battery management system (BMS).
Currently, in a commercial vehicle, when a relay is connected to battery packs used in the electric vehicle in order to supply a large amount of power, a voltage difference between the battery packs may be naturally balanced.
However, in the related art, it is difficult to control cell balancing, such that a voltage deviation between cells in the battery pack may not be narrowed, and when charging and discharging of the battery are conducted in a situation in which the voltage deviation between the cells in the battery pack is generated, the voltage deviation between the cells in the battery pack is intensified.